SUMMARY

Some snakes have a feeding regime characterized by the infrequent ingestion
of relatively large meals, causing impressive increments in post-prandial
metabolism. Metabolism remains elevated for many days, while digestion
proceeds, resulting in considerable investment of time and energy. Snakes
actively adjust thermoregulatory behavior to raise their body temperature
during digestion, exhibiting a post-prandial thermophilic response that
accelerates digestion at the expense of higher metabolic rates. In the present
study, we investigated the possibility that endogenously derived heat,
originating as a byproduct of the post-prandial increase in metabolism, could
itself contribute to the elevated body temperature during digestion in the
South American rattlesnake Crotalus durissus. We assessed heat
production, at a constant environmental temperature, by taking infrared (IR)
images of snakes during fasting and after being fed meals varying from 10% to
50% of their own body masses. Our results show clearly that digesting
rattlesnakes have significantly increased body temperatures, even when
precluded from adjusting their thermoregulatory behavior. The feeding-derived
thermogenesis caused the surface body temperature of rattlesnakes to increase
by 0.9–1.2°C, a temperature change that will significantly affect
digestive performance. The alterations in body temperature following feeding
correlated closely with the temporal profile of changes in post-prandial
metabolism. Moreover, the magnitude of the thermogenesis was greater for
snakes fed large meals, as was the corresponding metabolic response. Since IR
imaging only assesses surface temperatures, the magnitude of the thermogenesis
and the changes in deep core temperature could be even more pronounced than is
reported here.